The present invention pertains generally to the treatment of urinary incontinence and more particularly to an incontinent bladder control method and apparatus incorporating a prosthesis for selectively restricting urine flow in a urethra.
Both males and females have an external sphincter formed about the urethra which, when functioning normally, constricts the urethra and prevents flow of urine from the bladder except when the bladder is voided during normal urination.
Urinary incontinence may result from several causes. For example, in females stretching or lengthening of the pelvic attachments to the bladder and urethra (termed cystocele or urethrocele) may occur, such as following a normal vaginal parturition, thereby allowing the bladder to descend from a normal position (FIG. 1) into a lower position (FIG. 2) thus functionally shortening the urethra. This form of incontinence may be surgically corrected by re-securing the bladder and urethra into a normal or near-normal position in the pelvis (FIG. 3), thereby regaining normal or additional urethral length. In this type of incontinence, the essential elements of the sphincter are intact.
A more difficult form of urinary incontinence relates to iatrogenic injury to the urethral sphincter. Such injury is common in the male following certain types of prostate surgery (e.g., for prostate malignancy and sometimes for benign prostatic hypertrophy) and produces incontinence as result of damage to or loss of the external urethral sphincter. This form of incontinence is treated by repair or augmentation of the sphincter, or by substitution of its function by implantation of a prosthetic sphincter. It is not treatable by repositioning surgery, as in the case of female urethrocele/cystocele, because that surgery requires an intact sphincter.
There are numerous prior art prosthetic sphincters for selectively closing and opening the urethra to prevent incontinence. These devices typically incorporate an inflatable cuff which surrounds the urethra or encloses it on two sides, and which is inflated to restrict urine flow in the urethra. Examples of such prosthetic sphincters are seen in U.S. Pat. No. 4,571,749 to Fischell, U.S. Pat. No. 4,222,377 to Burton and in other prior patents referenced in the accompanying information disclosure statement.
Implementing this approach can encounter surgical difficulties and using it involves problems of control, both with potentially serious complications. Surgery in the female requires a difficult dissection behind the bladder neck and urethra, risking perforation of the adjacent vaginal wall. In males, dissection in this area encounters the prostate and rectum, risking rectal injury/fistula.
After implantation, control and maintenance of pressure in the cuff has been found to be difficult. Inadequate pressure (inflation) applied by such prior art devices may fail to occlude the urethra and thus permit continued incontinence. When sufficient pressure is applied, incontinence can be initially prevented but then may recur as result of partial tissue loss or necrosis of the urethra due to excessive localized pressure applied to the urethra by the prosthetic sphincter.
Another drawback associated with the prior art prosthetic sphincters, which are activated by transfer of an incompressible fluid, relates to the complex control systems used for inflating and deflating the sphincter. Examples of such prior art systems are seen in U.S. Pat. No. 4,571,749 to Fischell and in U.S. Pat. No. 3,744,063, which includes a fluidic control system for inflating and deflating an artificial sphincter that includes four check valves. Other examples are disclosed in the accompanying information disclosure statement. Accordingly, a need remains for a better way to treat urinary incontinence, particularly in males and in cases of iatrogenic injury to the external sphincter.